The present invention relates to the remote servicing of nuclear steam generators, and more particularly, to the ultrasonic inspection of the lower head area of a nuclear steam generator.
With the increasing concerns over scheduling and minimising exposure to workmen's radiation, utilities are looking for ways to improve tooling and techniques associated with the maintenance of steam generators. The use of nozzle dams to seal off the lower head area of a steam generator from the refueling pool of the nuclear reactor, has been used as a way of reducing outage time for maintenance, by permitting parallel activities at the refueling pool and within the drained steam generator.
Some nozzle dams are secured in place against a clamp ring that is, in effect, an integral part of the internal wall of the steam generator. Because the clamp ring was not originally intended to accommodate the high loads imposed by the nozzle dam in use, some concern has arisen regarding the need to inspect the region immediately surrounding the clamp ring. In particular, since the internal wall surface of the steam generator is clad with anti-corrosive material, and the clamp ring is welded to the clad, the desirability of confirming intimate bonding between the clad and the base metal in the region around the clamp ring, has grown in importance.
As with other steam generator inspection related techniques, it is desirable that this particular inspection be accomplished with a minimal radiation exposure to the operators, and in a relatively short period of time.